public function testCrawlSource()
{
$html = <<<HTML
\t\t\t<a href="http://pass.foo.com">Foo</a>
\t\t\t<a href="http://fail.bar.com">Bar</a>
\t\t\t<embed src="http://pass.embed.com"></embed>
\t\t\t<iframe src="http://pass.iframe.com"></iframe>
HTML;
$this->assertEquals(['http://pass.iframe.com', 'http://pass.embed.com', 'http://pass.foo.com'], $this->Crawler->crawl($html));
}